U.S. Pat. No. 5,549,382 describes a cooking hob provided with a support plate for supporting several cooking vessels. The support plate has several cooking areas and the cooking hob includes heating means for each cooking area and driving means aligned with one of the cooking areas. The driving means comprise a lower magnetic coupling member driven to rotate below the support plate in a position close enough to it to magnetically transmit torque to an upper magnetic coupling member attached to a stirrer located inside a cooking vessel placed in the corresponding cooking area. In one embodiment, the lower and upper magnetic coupling members include permanent magnets.
This magnetic coupling arrangement has several drawbacks. Firstly, when the user moves the vessel closer to the cooking hob, the vessel, containing the upper magnetic coupling member, is strongly attracted by the lower magnetic coupling member of the cooking hob, and this can cause the vessel to collide against the cooking hob with the risk of breaking the support plate. Secondly, the attractive force of the two lower and upper magnetic coupling members also makes removing the vessel from the cooking area of the cooking hob difficult to a large extent. Thirdly, when there is no vessel in the cooking area of the cooking hob, different kitchen utensils of a ferromagnetic nature can be involuntarily attracted towards the cooking area due to the magnetic field generated by the permanent magnets of the lower magnetic coupling member.